How to correctly override equals() method in Java?

General Discussions
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1

What is the correct way to override the equals method in Java?

I have a class People with two fields: name (a String) and age (an Integer). I want to properly override the equals method in Java to compare two People objects.

Here’s the code I tried:

public boolean equals(People other) {
    boolean result;
    if ((other == null) || (getClass() != other.getClass())) {
        result = false;
    } else {
        People otherPeople = (People) other;
        result = name.equals(other.name) && age.equals(other.age); // Error here
    }
    return result;
}

However, I get an error when calling age.equals(other.age), since equals() is typically used for objects like String, but age is an Integer.

How should I properly override the equals method in Java to handle this comparison correctly?

2

I’ve worked with Java for a while, and when dealing with custom objects, overriding equals() properly is key. I noticed you’re running into issues because you’re using equals() to compare age, which is an Integer. Since Integer supports equals(), your approach is mostly right, but the method signature needs to match Object, not People."*

Here’s the corrected version:

@Override
public boolean equals(Object obj) {  // Must accept Object, not People
    if (this == obj) return true;      // Same reference check
    if (obj == null || getClass() != obj.getClass()) return false;

    People other = (People) obj;
    return name.equals(other.name) && age.equals(other.age);  
    // Fix: age is an Integer, so equals() works properly
}

:white_check_mark: Why this works?

  • Uses Object as the parameter (necessary for correct overriding).
  • Compares name and age correctly using equals().
  • Includes a reference check (this == obj) for performance optimization.
3

That’s a solid implementation, @akanshasrivastava.1121! One way to make it even more readable and null-safe is by using Objects.equals() from Java’s java.util package. It automatically handles null checks, making the code cleaner and safer.

Here’s the improved version:

import java.util.Objects;

@Override
public boolean equals(Object obj) {
    if (this == obj) return true;
    if (obj == null || getClass() != obj.getClass()) return false;

    People other = (People) obj;
    return Objects.equals(name, other.name) && Objects.equals(age, other.age);
}

:white_check_mark: Why use this?

  • No need for explicit null checks—Objects.equals() does it for you.
  • More readable, especially when comparing multiple fields.

:bulb: This approach enhances your java override equals implementation with better readability and safety.

4

Great points, @netra.agarwal To follow best practices, it’s essential to override hashCode() alongside equals(). This ensures consistency when using collections like HashSet or HashMap.

Here’s the complete implementation:

import java.util.Objects;

@Override
public boolean equals(Object obj) {
    if (this == obj) return true;
    if (obj == null || getClass() != obj.getClass()) return false;

    People other = (People) obj;
    return Objects.equals(name, other.name) && Objects.equals(age, other.age);
}

@Override
public int hashCode() {
    return Objects.hash(name, age);
}

:white_check_mark: Why include hashCode()?

  • Ensures objects behave correctly in hash-based collections (HashSet, HashMap).
  • Maintains the contract between equals() and hashCode() to prevent unexpected behavior.

:bulb: By adding hashCode(), your java override equals implementation is now complete and collection-safe.